1. Field of the Invention
The present invention relates to a terminal for crimping an electric wire by compressional deformation, and further relates to a terminal-crimping mold for compressively deforming the terminal.
The present application is based on Japanese Patent Application No. Hei. 10-22294, which is incorporated herein by reference.
2. Description of the Related Art
FIG. 13 is a perspective view showing the shape of a terminal A before the terminal is crimped to an electric wire W. An electric-wire clamping portion 2 is provided on one end side (on the right side in FIG. 13) of a base plate 1 of the terminal A, and an electric contact portion 3 is provided on the other end side (on the left side in the drawing) of the base plate 1.
The electric-wire clamping portion 2 includes a conductor crimping portion 4 and a sheath clamping portion 5. The conductor crimping portion 4 has a pair of crimping pieces which are projected up from the opposite sides of the base plate 1, while the sheath clamping portion 5 has a pair of clamping pieces which are projected up from the opposite sides of the base plate 1. Each of the conductor crimping portion 4 and the sheath clamping portion 5 is U-shaped in section. The lower portion of the conductor crimping portion 4 and the lower portion of the sheath clamping portion 5 are integrated, on the opposite sides, with a pair of side walls 6 and 6 which are erected up from the opposite sides of the base plate 1.
FIG. 13 shows the case where the electric contact portion 3 is of a female type. Upper end portions of a pair of side walls 7 erected from the opposite sides of the base plate 1 are further bent inward to form a rectangular pipe portion 8 with the base plate 1. A tongue piece 9 extended at the forward end of the base plate 1 is bent back into the rectangular pipe portion 8. If a male terminal (not shown) is fittingly inserted into a space of the rectangular pipe portion 8 above the tongue piece 9, the male and female terminals are electrically connected to each other.
A pair of side walls 10 erected up from the opposite sides of the base plate 1 are connected between the respective lower portions of the side walls 7 of the electric contact portion 3 and the side walls 6 of the conductor crimping and sheath clamping portions 4 and 5.
The electric wire W is connected to the terminal A is such a manner as follows. An insulating sheath 11 at an end of the electric wire E is stripped to expose a conductor portion 12. The conductor portion 12 is inserted in the conductor crimping portion 4 and the insulating sheath 11 is inserted in the sheath clamping portion 5. Then, both the conductor crimping portion 4 and the sheath clamping portion 5 are pressed so as to be narrowed from the outside. As a result, the conductor crimping portion 4 and the sheath clamping portion 5 are plastically deformed, so that the conductor crimping portion 4 is crimped to the conductor portion 12 and the insulating sheath 11 is held by the sheath clamping portion 5 (see FIG. 14).
The diameter of the insulating sheath 11 is larger than the diameter of the conductor portion 12. Accordingly, before the electric wire W is clamped, the distance between the pair of clamping pieces of the sheath clamping portion 5 is larger than the distance between the pair of crimping pieces of the conductor crimping portion 4 so that a portion 1a of the base plate 1 which serves as the bottom of the sheath clamping portion 5 is slightly projected down (see FIG. 13).
Accordingly, the upper surface of a lower sheath mold part 14 on which the sheath clamping portion 5 is placed is lower in level than the upper surface of a lower conductor mold part 13 on which the conductor crimping portion 4 is placed (see FIG. 15).
The crimping mold B for pressing and narrowing the electric-wire clamping portion 2 (the conductor crimping portion 4 and the sheath clamping portion 5) is arranged as shown in FIG. 15. The lower conductor mold part 13 and the lower sheath mold part 14 are disposed so as to be adjacent to each other. An upper conductor mold part 15 and an upper sheath mold part 16 which are driven to move up and down by a pressing apparatus are provided above the lower conductor mold part 13 and the lower sheath mold part 14 respectively.
A pair of moving guide pieces 15a which are projected down are provided in the upper conductor mold part 15 (only one piece 15a is shown in FIG. 15). When the upper conductor mold part 15 moves up and down, the moving guide pieces 15a slide on the opposite side surfaces of the lower conductor mold part 13.
A pair of moving guide pieces 16a which are projected down from the upper sheath mold part 16 slide on the opposite side surfaces of the lower sheath mold part 14 similarly to the moving guide pieces 15a.
The terminal A is placed so that the conductor crimping portion 4 and the sheath clamping portion 5 are located on the lower conductor mold part 13 and the lower sheath mold part 14 respectively. The conductor crimping portion 4 is crimped between the upper conductor mold part 15 which is moved down and the lower conductor mold part 13. The sheath clamping portion 5 is crimped between the upper sheath mold part 16 which is moved down and the lower sheath mold part 14.
Because the quantity of displacement of the conductor crimping portion 4 crimped thus is different from the quantity of displacement of the sheath clamping portion 5 crimped thus, one of the side walls 6 is pulled toward the conductor crimping portion 4 and the other is pulled toward the sheath clamping portion 5.
Further, because the electric contact portion 3 is not deformed at all, a large force for pulling the conductor crimping portion 4 acts on one of the side walls 10 and a force for preventing the pulling acts on the other of the side walls 10.
Because the height of the side walls 10 is lower than the height of the electric contact portion 3 and than the height of the conductor crimping portion 4, a neck portion 17 is formed between the electric contact portion 3 and the conductor crimping portion 4 (see FIG. 16).
If the height h.sub.1 of the side walls 10 is increased in order to reinforce the strength of the neck portion 17, cracks C occur because the height h.sub.1 of the side walls 10 is larger than the height h.sub.2 of the conductor crimping portion 4' after clamping to make local stress concentrated in upper end portions of the side walls 10 at the time of clamping (see FIGS. 17A and 17B).
Accordingly, there is a problem that the height h.sub.1 of the side walls 10 cannot be increased enough to reinforce the neck portion 17.